1. Field of the Invention
The present invention relates to a copying machine having a document presser plate and an automatic document feeder on a document support table.
2. Description of the Prior Art
Various types of copying machines are known in which an openable closure body having a document presser plate and an automatic document feeder is disposed over a document support table known as "contact glass" for placing a document thereon, the closure body being openable and closable over the document support table. There is a mode of operation in which only the document presser plate is used and the automatic document feeder is not used. When the closure body is to be opened and closed in such an operation mode, a large manual force is required since the automatic document feeder must also be moved with the closure body.
In view of the above problem, there has been proposed a copying machine structure having an automatic document feeder disposed separately from a document support table that is reciprocally movable with a book-like or sheet-like document placed thereon. In such a copying machine structure, exposure optical systems are associated respectively with the document support table and the automatic document feeder, or alternately, driver means are provided for the document support table and the automatic document feeder, respectively, for reciprocating movement thereof. This arrangement is however complex and requires a large number of parts which make the copying machine less reliable and also render its servicing less efficient. Another problem is that the exposure optical systems and the driver means take up a large space, resulting in an increased overall size of the copying machine.
A different copying machine has also been proposed in which an automatic document feeder of an integral construction is disposed on a document support table in a position outside of the range in which a document presser plate is openable and closable. The automatic document feeder includes a driver means for controlling operation of the automatic document feeder. More specifically, the automatic document feeder includes a motor and a power transmission system for transmitting power from the motor to feeder rollers, the power transmission system including a clutch. The motor is electrically connected by cables to a power supply and a control unit within the copying machine. When the automatic document feeder is reciprocally moved with the document support table, the cables tend to creep and may be cut off. The cables are required to be so arranged that they are not exposed outside of the copying machine.
In addition, the clutch included in the power transmission system comprises an expensive electromagnetic clutch for selectively transmitting and cutting off the motor power. Therefore, the cost of the copying machine is high.